program eptst;
{$I-}
const printer = 6;
      bell = 7;
      bs = 8;
      cr = $D;
      lf = $A;
      tab = 9;
      esc = $1B;
      CtlAT = 0;
      CtlA  = 1;
      CtlB  = 2;
      CtlC  = 3;
      CtlD  = 4;
      CtlE  = 5;
      CtlF  = 6;
      CtlG  = 7;
      CtlP  = $10;

       BoldBit =  $01;
       StrkBit =  $02;
       UnLnBit =  $08;
       SpScBit =  $10;
       SbScBit =  $20;

type byte = -128..127;

var b : byte;
    ior,i,eflags : integer;
    BD, SP, SB, UL, SO : boolean;

function cnv(i : integer) : byte;
begin
    if i >127 then cnv := i - 256
              else cnv := i;
end; {cnv}

procedure display(ch : byte);
var ch1 : byte;
Begin
  if (ch>=0) and (ch<=$1F) and (NOT(ch in [bell,bs,lf,cr])) then
    {control char}
    if ch = esc then write('|ESC|')
    else if ch = tab then write('          ') {10 spaces}
         else write('^',chr(ch+$40))
  else if ch<0 then begin
          ch1 := ch+128;
          if (ch1>=0) and (ch1<=$1F) then
               write('|alt-^',chr(ch1+$40),'|')
          else write('|alt-',chr(ch1),'|');
          end
      else write(chr(ch));
End;{display}

procedure DoUnitStat;
var fc,p : integer;
Begin
  write('Enter function code : '); readln(fc);
  write('Enter parameter : ');readln(p);
  unitstatus(printer, p, fc );
End; {DoUnitStat}

procedure overstrike;
var ch : array [1..4] of byte;
begin
  ch[1] := esc;
  ch[2] := ord('O');
  write('Enter 1st char : '); unitread(1,ch[3],1); writeln;
  write('Enter 2nd char : '); unitread(1,ch[4],1); writeln;
  unitwrite(printer,ch,4);
end;{overstrike}

procedure propspace;
var ch : array [1..4] of byte;
    n : integer;
begin
  ch[1] := esc;
  ch[2] := ord('P');
  write('Enter # of chars: '); readln(n);
  if n > 255 then
    begin
    writeln('to many chars');
    exit(propspace);
    end
  else ch[3] := cnv(n);
  write('Enter # of pads : '); readln(n);
  if n > 255 then
    begin
    writeln('to many pads');
    exit(propspace);
    end
  else ch[4] := cnv(n);
  unitwrite(printer,ch,4);
end;{propspace}

procedure bold;
var ch : array [1..3] of byte;
Begin
 ch[1] := esc;
 ch[2] := ord('e');
 BD := NOT BD;
 if BD then {turn on}
    begin
    eflags := eflags + BoldBit;
    ch[3] := cnv(eflags);
    end
 else  {turn off}
    begin
    eflags := eflags - BoldBit;
    ch[3] := cnv(eflags);
    end;
 unitwrite(printer,ch,3);
end;{bold}

procedure under;
var ch : array [1..3] of byte;
Begin
 ch[1] := esc;
 ch[2] := ord('e');
 UL := NOT UL;
 if UL then {turn on}
    begin
    eflags := eflags + UnLnBit;
    ch[3] := cnv(eflags);
    end
 else  {turn off}
    begin
    eflags := eflags - UnLnBit;
    ch[3] := cnv(eflags);
    end;
 unitwrite(printer,ch,3);
end;{under}

procedure strkout;
var ch : array [1..3] of byte;
Begin
 ch[1] := esc;
 ch[2] := ord('e');
 SO := NOT SO;
 if SO then {turn on}
    begin
    eflags := eflags + StrkBit;
    ch[3] := cnv(eflags);
    end
 else  {turn off}
    begin
    eflags := eflags - StrkBit;
    ch[3] := cnv(eflags);
    end;
 unitwrite(printer,ch,3);
end;{strkout}

procedure super;
var ch : array [1..3] of byte;
Begin
 ch[1] := esc;
 ch[2] := ord('e');
 SP := NOT SP;
 if SP then {turn on}
    begin
    eflags := eflags + SpScBit;
    ch[3] := cnv(eflags);
    end
 else  {turn off}
    begin
    eflags := eflags - SpScBit;
    ch[3] := cnv(eflags);
    end;
 unitwrite(printer,ch,3);
end;{super}

procedure subsc;
var ch : array [1..3] of byte;
Begin
 ch[1] := esc;
 ch[2] := ord('e');
 SB := NOT SB;
 if SB then {turn on}
    begin
    eflags := eflags + SbScBit;
    ch[3] := cnv(eflags);
    end
 else  {turn off}
    begin
    eflags := eflags - SbScBit;
    ch[3] := cnv(eflags);
    end;
 unitwrite(printer,ch,3);
end;{subsc}

BEGIN
writeln('Enter text to be sent to printer.');
writeln('Ctl @ = unitstatus.');
writeln('Ctl A = overstrike;');
writeln('Ctl B = strkout;   ');
writeln('Ctl C = bold;      ');
writeln('Ctl D = under;     ');
writeln('Ctl E = super;     ');
writeln('Ctl F = subsc;     ');
writeln('Ctl P = propspace; ');

b := 0; eflags := $40;  {bit 6 is always on}

BD := FALSE;   {BOLD}
SP := FALSE;   {SUPERSCRIPT}
SB := FALSE;   {SUBSCRIPT}
UL := FALSE;   {UNDERLINE}
SO := FALSE;   {STRIKEOUT}

repeat
   unitread(2,b,1);
   display(b);
   for i := 1 to 20000 do;
   case b of
      CtlAT : DoUnitStat;
      CtlA  : overstrike;
      CtlB  : strkout;
      CtlC  : bold;
      CtlD  : under;
      CtlE  : super;
      CtlF  : subsc;
      CtlP  : propspace;
      Otherwise : unitwrite(printer, b, 1);
      end;
   ior := IORESULT;
   if ior <> 0 then writeln('I/O error = ',ior:1);
   until(b=CtlG);
END.